Kepler Center for Astro and Particle Physics
Eberhard Karls Universitat Tubingen, Germany
Kepler Kolloquium
‘‘Low-Energy Neutrino Detection through
Neutrino-Nucleus Interaction Probes’’
T.S. Kosmas
Division of Theoretical Physics, University of Ioannina, GR-45110, Greece
•
Low-energy Neutrino production Sources
•
Neutrino Detection
•
Neutrino-Nucleus Interactions
¾ Coherent Neutrino-Nucleus Scattering
¾ Inelastic Neutrino-Nucleus Scattering
Collaborating Groups:
University of Ioannina, Greece : V. Tsikoudi, J. Sinatkas, V. Stavrou
K. Balasi, V. Tsakstara, G. Karathanou,
P. Giannaka, J. Kardaras
Hellenic Army Academy, Greece: P.C. Divari, Th. Liolios
Univ. of Tuebingen, Germany
: Group of A. Faessler
T. Univ. of Darmstadt, Germany : Group of J. Wambach
Univ. of Jyvaskyla, Finland
: Group of J. Suhonen
Univ. of Valencia, Spain
: Group of J.W.F. Valle
RCNP, Univ. of Osaka, Japan
: H. Ejiri (MOON-experiment)
T.Univ Dresden, Germany
: K. Zuber (COBRA-experiment)
Important neutrino production sources
1) Laboratory Neutrino Sources
i. Reactor neutrinos (Low-Energy neutrino beams)
¾ Slow – pion and muon decay (E < 52.8 MeV)
¾ Beta decay (E < 10 MeV)
ii.
Accelerator neutrinos (High-Energy neutrino beams)
¾ Boosted beta-beam neutrinos (E < 100 MeV and more)
¾ Long (short) baseline neutrinos
2) Astrophysical Neutrino Sources
i.
Solar Neutrinos (E < 20 MeV)
ii. Supernova Neutrinos (E < 60 - 80 MeV)
iii. Atmospheric Neutrinos (E < a few GeV)
iv. Gamma-Ray-burst neutrinos, Cosmological Neutrinos, etc.
Reactor neutrino sources
Reactor neutrino beams used to study low-energy neutrino interactions and
neutrino oscillations (KARMEN, LSND, BooNE, etc. ):
slow-pion decay
μ-decay (at rest)
π + → μ + +ν μ
μ + → e+ +ν e +ν μ
π − → μ − +ν μ
μ − → e− + ν e +ν μ
Neutrino distributions
n
νe
(εν e ) =
96εν2e
4
mμ
(mμ − 2εν e )
32εν2μ 3
(ε ν ) =
( mμ − 2ε ν )
4
νμ
μ
μ
mμ 2
n
Reactor Neutrinos for low-energy interactions and neutrino
oscillations
The LSND (Liquid Scintillator Reactor Neutrino Detector) was designed to
search for the oscillation
ν μ → νe
and obtained evidence for flavor change at the scale
2
2
Δm ∼ 0.2 eV
Although KARMEN did not confirm the LSND results, a combined analysis
of the two experiments defines compatible regions:
W.C. Louis, Prog.Part. Nucl.Phys. 63 (09)51.
Both experiments used a high-intensity 800 MeV proton beam to produce a
−
+
−
large number of π pions which almost all decay ( π and the produced μ
are captured).
The BooNE neutrino detector (FNAL) is now also used for core
collapse SN searches : [astro-ph/09103182v1]
Low-energy Beta-beam neutrinos
Recently, the use of boosted β-decay radioactive nuclei
was proposed* to produce neutrino-beams of low energy
(beta-beam neutrinos).
With this facility we obtain an intense, collimated and
pure neutrino-beam for searching Neutrino–Nucleus
Interactions.
Such studies are important for various open issues in
nuclear, particle physics, and astrophysics.
Low-energy Beta-beam neutrinos are useful for the
interpretation of SN’ν signals.
* C. Volpe, J. Phys. G, 30 (2004) L1–L6
Beta-beam neutrinos (radioactive sources)
Small Storage ring-detector
I(18Ne)=2.7x1012 ions/s
18
10
Ne → 189 F + ν e + e +
+
α
νe
β
θ
e
r
d=10 m
D=678 m
h=15 m
νe
18Ne
18Ne
boost
J. Serreau, C. Volpe: Phys.Rev. C70 (2004) 055502
νe
Energy-spectra of Boosted beta-beam neutrinos
0,10
γ=3
nbeta-beam(εν)
0,08
0,06
0,04
0,02
γ = 15
0,00
0
20
40
εν
60
80
( M eV )
For the interpretation of low-energy interactions (SN neutrinos, etc.)
The distributions refer to 18Ne but there are similar for 6He too.
γ < 15
Solar Neutrinos
Neutrinos produced by the thermonuclear
reactions in the Sun
Underground Neutrino detection Experimen.
(Homestake, GALLEX, SAGE, SK, SNO, etc.)
Measurements of solar neutrinos (KAMLAND, Borexino, etc. )
used to test the standard solar model (SSM).
Recent probes, SNO+ experiment, aim to measure low-flux solar neutrinos
(pep, CNO-cycle neutrinos) to check the abundances of solar core and clarify if
the metallicity in the Sun is homogeneous
[K. Zuber, Inv. Talk, medex09].
The liquid scintillator detector of SNO+ experiment will be able to study lowenergy solar neutrinos, geo-neutrinos, reactor neutrinos, supernova neutrino
pp-chain reactions
Qν= 1.442 MeV
Qν ≤ 0.420 MeV
99,77%
0,23%
p + p → d+ e+ + νe
84,7%
d+p→
7Be
3He+3He→α+2p
3He
~2×10-5 %
+γ
13,8%
3He + 4He →7Be + γ
13,78%
pp I
p + e - + p → d + νe
+ e- → 7Li + νe
7Li
+ p ->α+α
pp II
0,02%
7Be
8B
+ p → 8B + γ
→ 8Be*+ e+ +νe
2α
Qν <15 MeV
pp III
3He+p→α+e+
+ νe
Qν≤ 18.77MeV
hep
The CNO cycle
2nd and 3rd generation stars like our Sun contain heavier elements
(C,N,O,etc) (formed after the explosion, matter ejection of older stars)
13N
→ 13C + e+ + ve
( ≤ 1.199 MeV)
15O
→
15N
+ e+ + ve
(≤ 1.732 MeV)
17F
→
17O
+ e+ + ve
(≤ 1.739 MeV)
Solar Neutrino fluxes (SSM)
Core-collapse Supernova Neutrinos
The energy-spectra of neutrinos emitted in a core collapse SN can be
approximated as
SN Energy spectra
The Mean Energy of the SN spectra
reflect the Temperature of the
burning shell from where they
escaped
Ε
≈ 1 1M eV
ve
−
Ε ve
≈ 16 M eV
Ε
≈ 25M eV
vμτ
Parameterization of SN-v energy-spectra
In modeling core-collapse SN and studies of nuclear response to
SN-ν, various parametrizations are used :
Fermi-Dirac
distribution
T = Neutrino Temperature α = Chemical Potential
Power-Law distribution for SN-v
The SN-ν energy-spectra can be accurately parameterized with a
power- law distribution of the form
α
⎛ εν ⎞
PL ( εν , εν , α ) = ⎜
⎟ e
⎝ εν ⎠
<εν > = the average neutrino energy
α = spectral pinching parameter
These parameters allow to adjust the width w
w=
εν − εν
2
2
−( a +1)
εν
εν
Beta-beam neutrino Energy-spectra for SN-v
The low–energy beta-beam neutrinos can be exploited to interpret
a SN–ν signal
Linear combinations of normalized beta-beam spectra are used
N
nNγ (εν ) = ∑αi nγ i (εν )
i =1
The fitting of coefficients αi and boost factors γi to a SN-neutrino
spectrum is achieved by minimizing the integral
∫ε dεν n (εν ) − n (εν )
ν
Nγ
SN
Neutrino-nucleus interactions
During the last decades, neutrino-nucleus interactions, β-decay modes, nuclear
μ-capture, etc., have deepen our knowledge on :
1) the fundamental electro-weak interactions
2) our understanding on nuclear structure
Such precious information inspired significant probes within and beyond the SM
and provided valuable interpretations to experiments looking for:
1) neutrino detection probes
2) Neutrino oscillation probes
3) neutrino masses …….
Neutrino–nucleus reactions play important role in astrophysical
processes (SN nucleo-synthesis, etc.).
Uncertainties on astrophysical interactions of neutrinos raised
numerous questions, still unanswered.
Our knowledge is limited by the understanding of neutrino-nucleus
cross sections based on reliable interaction Hamiltonians and w-f.
Theory of Neutrino-nucleus interactions
NC: Neutral current interaction (mediated by the Z-bozon)
CC: Charged-currents interaction (mediated by W+ or W- bozon)
νμ CC Event
NC Event
νe CC Event
Neutrino-Nucleus reactions
There are four types of ν-nucleus reactions for ν-detection
ƒ Charged-current reactions (l= e, μ, τ)
ƒ Neutral-current reactions (Coherent Channel Possible)
Coherent ν–Nucleus processes
For low-energy neutrinos (solar neutrinos), the coherent channel
dominates the total cross section (tsk, et al., NPA, submitted).
Coherent ν–Nucleus scattering (Neutral-Currents)
• The Coherent differential cross section reads
Φ = scattering angle, θW =Weinberg angle, Ev = incoming-neutrino energy
• Nucleons contribute coherently (coherent process dominates)
Nuclear recoil
In
experimental studies of Coherent neutrino-nucleus
scattering, the only observable is the average recoil energy
(i) Proportional to Eν2 , inversely proportional to A (mass number)
(ii) Including other experimental criteria, 28Si, 32S best choices
The calculations start from the quantity dσ/dTA
q2 = TA2 + 2AmN TA
Coherent neutrino-nucleus scattering
with
The quantity Qw is
Finally one needs the neutron density of the target
Coherent neutrino-Nucleus Scattering probes
X +
ν
ν+
X
Such studies could be
done in conjunction
with direct detection
of Cold Cark Matter
(cryogenic detectors).
Counting rates for Coherent Neutrino-Nucleus Scattering.
The Reactor-Neutrino flux is 1 0 1 3 cm − 2 sec − 1
Direct CDM detection: CDM-particle Scattering off nuclei
The Content of the universe:
Dark Energy ≈ 73%, Atoms ≈ 4%
Cold Dark Matter ≈ 23% (
LSP-nucleus scattering
χ + (Α, Ζ)
χ’ + (Α,Ζ)*
A) Coherent process is possible : Vector & Axial-Vector Currents
B) Dominance of Axial-Vector contributions
73Ge,
(Odd-A nuclear targets :
127I, 115In, 129,131Xe)
Signals of CNN scattering and direct detection of WIMPs
The energy transfer is very low (30-40 keV)
Inelastic ν–Nucleus scattering (Cross section)
In Walecka-Donnely method
[PRC 6 (1972)719, NPA 201(1973)81]
where
1st sum = Coulomb-Longitudinal contr.
2nd sum = Transverse contr.
One of the goals is: To investigate the Response as lowenergy neutrino detectors of :
i) Te, Cd, Zn –isotopes (COBRA ββ-decay experiment)
ii) Mo-isotopes (MOON ββ-decay experiment)
i) K.Zuber, Phys. Lett. B 571(03)148, talk at MEDEX-09, June 15-19, 2009, Prague.
ii) H. Ejiri, Phys. Rep. 338 (2000)265; H. Ejiri et a., Phys.Lett. B 530 (02)265;
Compact expressions for the 7-basic reduced ME
For H.O. basis, all basic reduced ME take analytic compact forms
The Polynomials of even terms in q have constant coefficients as
V.Chasioti, TSK, Czech. J. Phys. 52 (2002)467; Nucl. Phys. A, 829 (2009) 234
Advantages of the above formalism (FORTRAN Code) :
(i) The coefficients PJ are calculated once (reduction of computer time)
(ii) They can be used for phenomenological description of ME
(iii) They are useful for other bases sets (expansion in HO wave-functions)
Neutrino-nucleus cross sections
A). On the basis of the original calculations we could
study:
i) State-by-state calculations of dσ/dΩ
ii) The contribution of the individual multipolarities
iii) Dominance of Axial-Vector contributions in σ
B). Nuclear detector response to ν-sources:
i) solar neutrino spectra
ii) SN neutrino spectra
iii) reactor neutrino spectra
State-by-state calculations of dσ/dΩ
98Mo
V.Chasioti, TSK,
NPA 829 (09) 234
Dominance of Axial-Vector contributions in σ
98Mo
Summary and Outlook
(i)
Low-energy neutrinos searches
i.
Solar, SN neutrinos
ii.
Reactor and Beta-beam neutrino
Require: a). Reliable neutrino-nucleus reaction cross sections and
b). The Response Nuclear ν-detectors to various ν-spectra
(ii) Recent and future nuclear-recoil experiments, with very low-threshold
energy, could measure Coherent Neutrino-Nucleus Scattering in
conjunction with experiments of Direct detection οf CDM particles
and oν-double-beta-decay.
Ioannina, the city of Silver and Gold
Thank you for your attention